One serviceman was killed instantly and a second died from his wounds in hospital, according to a ministry statement quoted by Russian news agencies.
The soldiers were travelling with a convoy that was hit by "mortar fire from IS terrorists", according to the ministry.
Moscow announced earlier today that it was providing support to Syrian government forces in their push to take Deir Ezzor, one of the last remaining cities controlled by the jihadists.
It also has a troop presence on the ground and the two soldiers reported killed on Monday bring to 34 the number of Russian service personnel killed in Syria, according to defence ministry figures.